Proportional control power to boiler

[PGoose]

Is it possible to let Domoticz control the power with a device like a Sensata Crydom PMP Proportional Control SSR, so that you only send a surplus of power from solar panels to the boiler. I want to prevent feeding back into the grid. Does anyone have experience with this and are there alternatives?

[psubiaco]

Solid state relay is not a solution: if you have a 1500W resistor and you want to sends only 400W or 600W or 800W (depending by your solar panel extra production), you need to lower the voltage at the resistor side, using an AC/AC converter: even triac dimmer-style regulator is not good, because you have in-rush currents and harmonic distortion.
If you have a boiler with 2 resistors, you can make a circuit with few relays to supply
* the two resistors in serie (0.5x resistor power)
* only one resistor (resistor power)
* both resistors (2x resistor power)
This is my opinion.
Paolo

[HvdW]

I agree with @psubiaco
However in a basic script where you start gathering the solar output and the P1 power consumption data you could try:

Code: Select all

     if (SunnyPower >= 2600  then  -- or > 1000 or > 1500 or.....
                domoticz.devices('Boiler').switchOn()
                domoticz.notify('Boiler', "is heating from the sun",PRIORITY_NORMAL)
            end
            if (PowerConsumption >= 1000 then -- or > 500
                domoticz.devices('Boiler').switchOff()
                domoticz.notify('Boiler', "charging is idle",PRIORITY_NORMAL)
            end

Besides it sometimes is simple calculating.
In the Netherlands where we have 'salderen' one can leave it like it is and heat the boiler @night when electricity prices are low.
@daytime it is economically better to return the surplus to the net because every kWh delivered is a kWh less to be payed for buying expensive daytime electricity.